Method for can electrodeposition

ABSTRACT

A METHOD FOR AUTOMATIC ELECTRODEPOSITION WHICH ELECTRODEPOSITS A COATING ONTO A CAN BODY. THE CAN BODY IS PASSED ALONG A RING-SHAPED TROUGH WHICH IS FILLED WITH COATING SOLUTION AND AN ELECTRIC POTENTIAL IS APPLIED BETWEEN THE SOLUTION AND THE CAN BODY TO DEPOSIT A COATING ONTO THE CAN BODY. THE CAN BODY IS DIPPED INTO THE TROUGH AND IS MOVED ALONG IN THE TROUGH A DISTANCE SUFFICIENT TO ALLOW THE DESIRED AMOUNT OF COATING TO COVER THE INSIDE AND OUTSIDE OF THE CAN BODY. D R A W I N G

S pt. 26 1972 Y E. J. FlALA METHOD-FOR CAN ELECTRODEPOSITION OriginalFiled June 2, 1969 2 Sheets-Sheet l INVENTOR EDWARD J. FIALA BY v ATT'Y.

Sept. 26, 1972 E. J. FIALA. 3,694,336

' METHOD FOR CAN ELECTRODEPOSITION Original Filed June 2, 1969 2Sheets-Sheet 2 INVENTOR EDWARD J. F IA LA ATT'Y United States Patent C)3,694,336 METHOD FOR CAN ELECTRODEPOSITION Edward J. Fiala, Oak Lawn,Ill., assignor to Continental Can Company, Inc., New York, N.Y.

Original application June 2, 1969, Ser. No. 829,412, now Patent No.3,647,675. Divided and this application May 26, 1971, Ser. No. 147,003

Int. Cl. B01k /02; C23h 13/00 US. Cl. 204181 3 Claims ABSTRACT OF THEDISCLOSURE This case is a division of co-pend'mg application Ser. No.829,412, filed June 2, 1969, now US. Pat. No. 3,647,675 in the name ofEdward J. Fiala, entitled Automatic Rotary Electrodeposition Apparatus,and assigned to the same assignee as this invention.

My invention is drawn to a method for automatic rotary electrodepositingmaterial onto cans, and specifically, a rotary electrodepositing methodfor depositing a coating on can bodies.

In the prior art, it has been the practice to dip can bodies into asolution, lift them out of the solution, and allow them to dry. Theapparatus of this method is exemplified by the patent to Kronquest, US.Pat. No. 2,206,778, and assigned to the assignee of the presentinvention.

It is an object of my invention to provide a method for automaticallycoating can bodies.

It is another object of my invention to provide a can body feed systemfor the automatic spacing of cans which are rapidly fed through thesystem by a conveyor, and to provide can spacing of the coated canbodies at discharge.

It is another object of my invention to give minimal surface contact ofthe coating apparatus with the can body before, during and afterdeposition of the surface coat.

It is a final object of my invention to provide a method forsynchronized feed of can bodies through a coating bath to give arelatively even coat inside and outside with complete coating of baremetal.

In brief, my invention is a method for automatic coating of cans inwhich a can feed timing spiral receives cans fed to it in a randomfashion and conducts these cans to a feed turret. From the feed turret,the can bodies are passed to a large horizontal wheel ha'ving pocketsand the can bodies move downward into a coating solution. As thehorizontal wheel turns, the coating material is electrolyticallydeposited onto the can body. The can body approaches a discharge turret,is lifted out of the solution by the discharge turret and conducts thecoated can body to the next operation.

The above and other objects will become apparent from the followingdescription and drawings in which:

FIG. 1 is a schematic diagram of a can feed system, can coating system,and can discharge system.

FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view along line 33 of FIG. 1.

Patented Sept. 26, 1972 FIG. 4 is a top sectional view of the slidetaken along line 4-4 of FIG. 3.

My method is best described by the operation of my machine which isdesigned to take its place in a can production line at a stage after thecan bodies have been formed. The following describes the operation ofthe machine and my method. A conveyor 1 such as a flat top chain,carries flanged cans 2 to the timing spiral 3 shown in FIG. 1. Thetiming spiral 3 passes the can bodies 2 into the feed turret 4. Thetiming spiral feed turret 4, main rotating wheel 5, and discharge turret6 are all synchronized to' facilitate passage of can bodies 2 through mymachine. The feed turret 4 is shown with 10 pockets around it. The feedturret 4 is rotated in a counter-clockwise direction to convey canbodies 2 to main rotating wheel 5. A guide 7 of some sort may be used tohold the can bodies 2 in the feed turret pockets 9'. The main rotatingwheel 5 rotates in a clockwise direction and has pockets 9 mounted alongits outer periphery. Along the lower outer periphery of the mainrotating wheel, as seen in FIG. 1, is a first outer guide 10. This outerguide 10 holds the cans 2 in the wheel pockets as they proceed alongtheir path and while the cans are being lowered into the coating liquid.The coating solution moves in the tank at about the same speed as theslides and pockets. There being little relative motion between the canand coating solution, there is a minimum amount of foam or bubbles.After the cans are lowered into the coating liquid, they are secured inplace on the main wheel in the wheel pockets 9 by the anodes whichsurround them so that as they are passed around the middle half of theouter circumference of the main wheel, they are passing through thecoating liquid. When the can body is under the surface of the coatingsolution, electric current is passed through the can in such a way thatcoating material is deposited on the can. This operation begins at about12. This process continues until the can body has reached point 13 wherethe current is discontinued, and the can body 2 starts its emergencefrom the coating liquid. By this time, a coat has been deposited on theinside and outside of the can body 2 and the turret pockets 9 with theirrespective can bodies start upward out of the solution. While the canbody is emerging from the liquid, an outer guide 14 holds the can bodyin the wheel pocket against the main rotating wheel. Finally, the canbody is conveyed to the area of the discharge turret. When the can bodycomes to the point 15, the can body is peeled oif the wheel by a fixedpermanent magnet 16 located at the discharge turret. The fixed permanentmagnet keeps the can body pulled up against the turret wheel until thecan body in its circular path has come approximately to the point -17where the conveyor :1 crosses the can body path as the can istransported by the discharge turret. When the can body comes to theconveyor, it is released by permanent magnet 16 and is carried away bythe conveyor to the next operation.

The coating composition used in my apparatus may be a Water-dispersedcoating composition, such as a partially neutralized acrylicinterpolymer and an amine-aldehyde condensation product or a polyepoxideor both. Examples of such interpolymers are found listed in the patentto Donald P. Hart, US. Pat. No. 3,403,088, and assigned to P.P.G.Industries, Inc.

It is noted that these protective coatings have high dielectricstrength, coat metallic articles completely, have eflicientelectro-depositing qualities, and result in cured films which are clear,glossy and have attractive appearance and good durability.

Details of the can pockets and can pocket supports are shown moreclearly in FIG. 2. When the can body 2 enters the wheel pocket, as shownin detail in FIG. 2, it is supported above and below by supportelements. As the can slides by the outer guide shown in FIG. 1, thisguide contacts only the outer flange of the can without touching the canbody.

In FIG. 2, the wheel pocket is in its upper position. This wheel pockethas two supports 18, 19 one above and one below, and the can 2 iscontained in between them. Can 2 touches the wheel pocket only at theedge of the can. In this way, the can surface exposed to coating is at amaximum. The position shown in FIG. 2 is the position of the slide 20 onthe slide support shaft 21 when the can has just entered the pocket ofthe main wheel. The can is in this position also just before it is aboutto exit from the pocket of the main wheel. In each of these cases, theroller 22 is in position at the top of the roller track 23 as shown. Theroller track 23 is part of the slide cam 24 and has a continuous pathvarying in amplitude from the top of the slide cam to the bottom of theslide cam. As the roller follows the roller track from the top of itspath to the bottom, the pocket is pushed down into the solution. As themain wheel rotates, the roller follows the roller track down the slidecam forcing the slide and the wheel pocket with the can body to descendto the bottom of the slide shaft. At the point that the can body is atthe bottom of the slide, FIG. 3, the can flange touches three anodes 11which are spaced around the can position so as to press somewhat againstthe flange 22 of the can. That is to say, the can body is a force-fitbetween the anodes. As this station with its can proceeds around theslide cam, the wheel pocket and can are lowered into the lowermostposition. Electric potential is applied across the cathode 25 to the canbody when the flange of the can makes electric contact with the anodes.Slip rings or some other conventional means mounted at the center of themain wheel provide a connector for electrical current from theelectricity source to the anodes and cathodes. The anode and cathode aremounted on an insulator member or support plate 26. The anodes andcathode stay in the solution and the only relative motion betweenelectrical conductive elements is at the slip rings. The can body ispress fitted down between the anodes when the slide cam is at the bottomof its shaft. As the can body slides down between the anodes, the sharpedge of the flange 22 cleans the contact area of the anode and a goodelectrical contact is maintained between the anode and the can flange.The non-contact surface of the anode is coated rather quickly byelectrolytic deposition. After the anode is coated, little or noelectrolytic deposition takes place on the anode, but only on thesurface of the can body.

By keeping the anodes and cathodes continually in the solution, only avery thin layer of coating material is applied to them, since the wetsolution does not dry on the electrodes.

When the can descends into the area between the anodes and touches thebare surface of one or more of the three anodes, the electric potentialfrom the can to the cathode becomes the same as the electric potentialbetween the anodes and the cathode. The surface area of the can isrelatively large and since the can is located somewhat nearer to thecathode than any of the anodes, and the anodes are coated, the can bodyreceives coating which is deposited on the bare surfaces of the can bodybecause of the electric potential across the cathode and the can. Thelength of the cathode is about coextensive with the can length. Theapplication of electric potential across the cathode and can body setsup an electric field between the cathode and anode to cause migration ofions from the cathode to the can body and consequent electrolyticdeposition of a coating material on the can body. Most of the coatingmaterial is deposited upon the inside of the can body. Fresh solution isassured because the can body is being swirled through the coatingsolution and currents are continually pasing through the interior of thecan body as well as by its exterior. The

exterior of the can receives some coating upon it from the ions of thecoating solution which are mixed with the electrically neutral coatingsolution located outside the can body.

When a can body has completed its coating cycle and has arrived at point13, FIG. 1, it will start its journey out of the solution. The can bodyflange 22 moves upward on the slide and when it clears the anode, theelectrical potential is disconnected between the can body and anode andno more coating material is deposited on the can because the can iselectrically neutral. Likewise, the discharge of current between theanode and cathode directly coats the anode with an insulating coatingand as soon as the three anodes have been coated on their can flangecontact spots, electric current will cease flowing from cathode to anodeat this station.

Alternatively, electric potential switching action may be applied acrossthe cathode and anode by means of limited segmented slip rings at thecenter of the main wheel. In any case, after the can is lifted, no moreelectrolytic deposition takes place across the anode and cathode until anew can body is press fitted down into the space between the anodes andthe can body is electrically connected to the anode and thus, to theelectric power source through the can flange and the bare spot on theanode. The coated can body is now lifted out of the solution and comesto the discharge turret. At this point, the can body is at the sameelevation as the discharge turret and the discharge turret magnet peelsoff the can body from the wheel pocket.

As pointed out in the description of FIG. 1, the coated can body istransferred smoothly into the discharge turret pocket and revolves withthe discharge turret 6. The outer guide 28 acts as a safety feature tohold can bodies to the discharge turret where the magnet fails. However,in normal operation, the coated can bodies do not touch the outer guide28 because it is essential to minimize scraping contact which mightcause the loss of coating from the can body.

The top view of the pocket and side of FIG. 4 shows the two slidesupporting shafts 21 upon which the pocket slides. The top plate 18 ofthe pocket and the bottom plate 19 of the pocket are shown one above theother. The anodes and cathodes are mounted in the insulating plate 26,and the insulating plate is shown as mounted and supported by verticalshaft 27 which is attached to the wheel as shown in FIG. 2.

Some of the advantages of my invention are that vertical entry of thecan body prevents air bubbles from forming within the can bodies, canbodies are uniformly separated in the deposition cycle, can bodies arecoated evenly and completely inside and outside, only the bareconductive metal of the can body is coated, little material is used, thesystem has an automatic electric on/oif feature, the solids of thecoating solution are kept in suspension by the stirring action of therotating slides and pockets, and the electrical system elements arefixed in position.

The foregoing is a description of the illustrative embodiment of theinvention, and it is applicants intention in the appended claims tocover all forms which fall within the scope of the invention.

What is claimed is:

1. A method of electrodepositing a coating solution onto a flanged canbody comprising:

moving said can body in a circular fashion about a central hub;

swirling said solution in a circular fashion in the same path as saidcan body and at the same speed as said can body;

lowering said flanged can body into said solution having anelectrodepositing material therein, whereby few bubbles adhere to saidcan body;

applying an electric potential between an anode and a cathode located insaid solution;

forcing the flanged can body down between spaced vertical anodes,whereby said anode and a can flange form an electrical contact; and

raising said flanged can body from said coating solution.

2. A method of electrodepositing a coating solution onto a flanged canbody as set forth in claim 1 in which the step of forcing said flangedcan comprises the steps of:

pushing said flanged can down between the anodes whereby the flange ofsaid can touches each said anode;

scraping the flange of said can body against the side of each said anodewhereby an electrical contact is established between said can body andsaid anode.

3. A method of electrodepositing a coating solution onto a flanged canbody as set forth in claim 2 in which the step of raising said flangedcan body comprises the steps of:

lifting said flanged can body from between said anodes whereby theflange and anode are electrically discon- References Cited UNITED STATESPATENTS Clayton et al. 204-181 Sumner et al. 204-181 Sumner et al.204-181 X Clayton et al. 204181 Jackson et al. 204-300 Bell et al.204-481 JOHN H. MACK, Primary Examiner A. C. PRESCOTT, AssistantExaminer US. Cl. X.R.

